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ASHP using its immersion, but I don't know why

Tufty · 2024-09-04T18:02:18Z

Hi all,Each month I check my meter readings - on the heatpump and also my consumer unit.Ive never needed to use the ASHP immersion heater, so that figure has been 0 for a couple of years. But since Jan 2024, the immersion has been using about 5kwh per month; and has been progressing to about 11kwh last month.It shouldnt be using any immersion (especially becuase I only have DHW on in the summer months!). It didnt for the 2 previous years. Theres been perhaps one or two times where Ive has to quickly heat some water becuase Ive had guests to stay, but apart from that I just let the heat pump heat the cylinder once every 48 hours, which is fine for my use. (I live alone).Is there a setting somewhere that may be using the immersion?Heres some photos which Im hoping gives you an idea of its current settings. Any guidance or insight would be gratefully received. Thankyou.

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Air Source Heat Pumps (ASHPs)

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Tufty

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Topic starter 05/09/2024 4:10 pm

@gary Thankyou. At the moment I have it heat to 55 once every 48 hours. I will reduce that to 50 and see if that stops the immersion from kicking in. As you say, perhaps I fiddled with it in Jan 2024.

@Johnmo . Thanks all good points. Ill post an update on here when I have one. Thanks 🙂

This post was modified 1 year ago by Mars

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Majordennisbloodnok

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05/09/2024 4:45 pm

@tufty, I can confirm my Ecodan is set up pretty similarly; tank target temperature is 52degC and will start heating once the actual temperature drops below 42degC. That's plenty hot enough for our showers, baths and general washing up, even taking into account the periodic taking of residence in the bathroom by youngest (teenage) offspring.

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Tufty

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Topic starter 06/09/2024 6:46 am

Morning guys.

Ive just been looking at the Ecodan. Ive reduced the DHW from 55 to 50 degrees. This is scheduled to happen once every 48 hours (as before).

Ive checked the immersion meter reading (it is separated out from the ASHP meter reading on my consumer unit). Its used 2kwh since sunday. The DHW came on monday and wednesday, and will do again today. This suggests that each time the cylinder heated this week, it needed to use 1kwh from the immersion.

I noticed that I have the DHW Max Operation Time set to 30 minutes. Not sure if that makes a difference? IE: Perhaps the Ecodan panics and thinks that its only got 30 minutes to heat the water up to 55 degrees, and so to achieve that within 30 minutes it uses the immersion? Just a thought.

Anyway, for now its set to 50 degrees. So Ill give it a few days and check the immersion meter reading.

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Gary

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06/09/2024 6:49 am

@tufty

Posted by: @tufty

↑

I noticed that I have the DHW Max Operation Time set to 30 minutes.

That will be your problem then, just change it to 2 hours, its using the immersion as you have restricted the run time of the heat pump to heat the water so after 30 mins the heat pump switches off and it turns on the immersion to get it to the target temp.

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Tufty

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Topic starter 06/09/2024 9:40 am

@gary Great - I shall do this today. 🙂

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Gary

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06/09/2024 9:48 am

@tufty Also make sure that you have the heating timer set up for that length of time as well otherwise the timer will cut it off as well but at least it won't try and use the immersion then it will just not get up to temp.

This one

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Tufty

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Topic starter 07/09/2024 7:35 am

Thanks @Gary - good idea. Ive just changed this setting to 2 hours. (it was at 1 hour). Cheers!

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Tufty

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Topic starter 19/09/2024 6:43 am

Morning guys

Just a quick update: My immersion hasnt kicked-in since I reduced DHW from 55 to 50, and increased DHW Max Operation Time from 30 minutes to 2 hours. So thats done the trick! Thanks so much.

Ive had to have a little word with myself: whats the point in keeping monthly stats if I dont notice that something like the immersion has been coming on since January! Ugh. Ive have been suitably self-admonished.

Anyway, thanks for your comments.

👍

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Mars

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19/09/2024 9:21 am

@tufty from what I understand, most low-temperature heat pumps can heat water up to around 45°C using just the heat pump itself. Anything above that typically requires the immersion heater, which might explain why it’s been kicking in when you’re trying to reach 55°C.

Nevertheless, I'm glad you've sorted it out.

For others that read this topic, your heat pump may be able to handle 50°C without using the immersion. If it still activates, consider lowering the hot water target to 45°C to avoid the immersion kicking in.

This post was modified 1 year ago by Mars

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Morgan

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19/09/2024 10:26 am

How does one discover/know if the immersion is being used?

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Mars

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19/09/2024 7:51 pm

@morgan It’s going to vary for everyone, but I see a significant spike in our SolarEdge app when the heat pump kicks in. Normally, our consumption for hot water heating via thevASHP sits around 3.5-4 kWh, but when the immersion heater activates, it jumps to over 5.5 kWh. I think it ultimately depends on how each person monitors their usage.

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